Hydraulic blank holder



Dec. 18,1928. 1,696,140

W. FERRIS HYDRAULIC BLANK HOLDER ed June 12, 1926 LYVENTOR. Mum/"Emu.

ATTORNEY.

Dea s, 1928.

1,696,140 W. FERRIS HYDRAULIC BLANK HOLDER Filed June 12, 1926 2 Sheets-Sheet 2 IXVENTOR. Mu TEE FEE/W61 A TTORNE Y.

employ an air Patented Dec. 18, 1928.

UNITED STATES.

PATENT oFFmE.

wan'rnn mains, o1- mwauxnn,

rm, O1 MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.

HYDRAULIC BLANK HOLDER.

Application fled June 12, 1926. Serial No. 115,487.

the blank is freed from the die. Mechanical devices capable of positive action have been resorted to in order to avoid this characteristic 'ump, but such devices are not entirely satis actory because of the complicated toggle movements ordinarily required to attain correct action of the ring.

One object of the present invention is the provision of a hydraulic pressure pad for effecting a thoroughly satisfactory action of the pressure ring. 7

Another object is the provision of a hydraulic pressure pad capable of applying a fully controllable blank. holding pressure.

Another object is the provision of a stripping mechanism capable of providing aheavy initial stripping force suflioient to break the formed piece from the die, followed by a more rapid, controlled stripping movement to complete the stripping operation and return the pressure ring to its initial position for the loading operation.

Another object is the provision of a unit for the purposes named in which the parts may be readily removed for inspection, replacement or repair.

Another object is the draulic'unit, involvin der, capable of handfi provision of a. hya piston and cylinng'within itself the transfer of large quantities of liquid with sufficient rapidityto maintain the cylinder flooded during rapid movements of the piston.

Other objects and advantages will appear from the following description of an illustrative embodiment ofthe present invention.

In the drawings r Figure 1 is a sectional view of a draw press equipped with a blank'holder embodying the present invention.

Fig.2 is a lonmtudinal sectional view, on a larger scale, of a hydraulic pressure pad pressure taken substantially Figure 1. t

Fig. 3. is a fragmentary sectional view similar to Figure 2, with the parts in different operating positions. The hydraulic pressure pad of the present invention may be applied to presses of various types or forms. Flgure 1 comprises the usual bed 10, supalong the line 2'-2 of porting a bolster ll, beneath a crank oper ated ram 12. The ram 12 carries a female WISCONSIN, ASSIGNOR TO THE OILGEAB COH- The press shown in die 13 for cooperation with a male die 14 fixed to the bolster 11. A pressure ring 15 of standard type surrounds the male die and is supported by a series of upright knockout pins 16, projecting through and loosely guided in the bolster. The pins 16 are supported by a pressure plate 17 disposed within an opening 18 formed in the bed 10 and constituting part of a hydraulic pressure pad such as will now be described.

The pressure pad selected for illustration comprises a pressure sustaining member in the form of a main pot casting 19 supported beneath the press bed by means such as hanger bolts 20. The'casting 19 is formed with a thick bottom 21 and an upstanding rim 22 cooperating to provide an open basin or reservoir 23. An overflow opening 24 determines the level of liquid inv .the reservoir.

The pressure plate 17 is supported by a plurality of plungers 25 mounted for vertical reciprocation in" appropriate cylinders 26 fixed in the-pot casting. Each cylinder26 is mounted over and in alignment with an appropriate cored opening 27 formed in the bottom 21 of the casting. In this instance, four plungers 25 are provided, symmetrically disposed with respect to the pressure plate 17. All of the cored openings 27 are in open communication thru ports 28 with a horizontal chamber 29 formed in the bottom 21 "of the casting. Chamber 29 is maintained flooded with liquid under pressure supplied thru a port 30 and pipe 31 from any appropriate source.

In this instance,

liquid is supplied to pipe 31 f rom a variable displacement, constant pump 32. of the type described in' the prior patent to Walter. Ferris, N 0. 1,578,233, issued March 23, 1926. It will sufiice here to say that this pump delivers liquid under constant pressure and at a rate which varies automatically with variations in demand from zero to the full ca acity of the pump. A check valve 33'in t e pipe line 31 protects the pump against excessive pressures that might be set up in chamber 29, and a high pressure relief valve 34 of appropriate form is connected to the pipe 31 between the check valve 33 and chamber 29 to determine the maximum pressures in the chamber. The valve 34 is controlled by a spring 35 whose tension may be varied by adjustment of the screw 36 to thereby determine the pressures at which the valve will open. The relief valve 34 discharges thru a pipe 37.

Two vertical cylindrical openings 38 are formed in the bottom 21 of the casting intersecting the chamber 29, and each contains a hollow cylinder 39 closely fitted therein but freely removable therefrom. Each cylinder 39 rests upon an internal shoulder 40 formed in the opening, and is provided with an annular channel 41 in open communication with the chamber 29. Ports 42 efiect communication between channel 41 and the lower end- 43 of each cylinder, the lower end being closed, preferably by a removable head 44. The lower portion 43 of each cylinder is normally separated from the main bore 45 thereof by a valve 46 having a flange 47 seated against an internal shoulder 48 formed in the cylinder. A spring 49 yieldably retains this valve in upper closed position. The upper ends of the cylinders are open to the reservoir 23 and are disposed somewhat below the liquid level therein so as to be flooded at all times.

A piston 50 is fitted for vertical reciprocation within the bore 45 of each cylinder, and each piston is attached to the pressure plate 17 preferably thru connections that atford ready adjustment between the pistons plate. In this instance each piston is provided with a shank 51 threaded to receive a capstan head 52 fixed to a rod 53 swivelcd in the plate. Each capstan head is preferably provided with a convex surface 54 seated against a concave face 55 on a spacer element- 56, between the plate and corresponding head, so as to permit slight relative displacement of the head without binding. The upper end of each piston 50 is also preferably slightly reduced as indicated at 57 to insure against binding within its cooperating cylinder. Any appropriate means, such as a ring 58 closely fitted in each cylinder and coacting with the beveled end 59 of the piston, may be provided for automatically centering each piston. The rings 58, in this instance, are yieldably held against the ends of the pistons by springs 60 held under compression by tension bolts 61 fixed to the pistons.

Each piston 50 is pierced longitudinally by a plurality of passages 62 in open communlcation with the reservoir 23 through the upper end of the cooperating cylinder. The

lower ends of these passages are normally closed, however, by a valve 63. Each valve shown comprises a disk (54 having a sleeve extension 65 slidably engaged in an appropriate bore 66 formed in the lower end of each piston. A spring (37 interposed between the head 68 of a rod 69 carried by each piston, yieldably retains each valve in upper closed position. The valve 46 hereinbefore mentioned is provided with a rim 70 adapted to be engaged by the under face of the valve 63 as the piston approaches the lower limit of its stroke, to thereby open valve (53 and expose the lower end of the bore 45 to the pressure in chamber 29.

Several discharge ducts 71 are provided in the wall of each cylinder intermediate the ends thereof. These ducts are preferably arranged in groups and communicate with a second horizontally disposed chamber 72 formed in the bottom 21 of the pot casting above the chamber 29. Chamber 72 communicates thru port 73 and pipe 75 with discharge pipe 37 hereinbefore mentioned, which pretcrably extends to a point well above the chainher so as to avoid draining the same. This chamber also communicates thru a passage 76 with the reservoir 23, this passage 76 being normally closed, however, by a check valve 77 yieldably held in its lower closed position by a spring 78 beneath bracket 79. The escape of liquid thru each group of ducts 71 is rest'ricted by a valve 80 intersecting these ducts and containing a group of orifices 81 adapted to register therewith. Each valve 80 is retained in assembled position by any appropriate means such as a set screw 82, an appropriate lug or projection 83 being provided by which each valve may be rotated to reduce or cut off the flow of liquid thru ducts 71.

Any appropriate means such as piston rings 84 and 85 are preferably provided about each cylinder 39 above and below the channel 41 in order to reduce leakage to a minimum. Any liquid that escapes past the rings 34 enters the chamber 72, and any liquid that escapes past the rings 85 enters chamber 813 in the bottom of each opening 33 beneath the cylinder. In order to avoid a building up of pressure in chambers 86, passages 87 are provided, which lead therefron'i to and thru a vertical passage 88 to the reservoir 23.

Figures 1 and 2 illustrate the positions of the parts prior to a drawing operation. The pressure plate 17 is held against the bottom of the bolster 11 by the upwa rd thrust of the several plungers 25, under the hydraulic pressure in the openings 27, transmitted from chamber 29 through ports 28. The knockout pins 16 are thus held in elevated position so that the pressure ring 15 is in position to receive the blank (1. The pistons 50 are also in elevated position, and the bores 15 of the cylinders are completely flooded with liquid tons 50 corresponds,

substantially at atmospheric pressure. The several parts retain these positions until the top die 13, in its descent, engages the blank (1 and forces the pressure ring 15 downwardly on the draw stroke. This downward movement of the pressure ring 15, transmitted through the knockout pins 16 and pressure plate 17 to the plungers 25 and pistons 50, is resisted by the hydraulic pressure in the openings 27 andby the bodies of liquid contained in the bores of the cylinders 39. The blank is thus firmly gripped between the top die and the pressure ring 15. The lowering of the plungers 25 immediately increases. the pressure in openings 27 and chamber 29, so thatcheck valve 33 closes, relief valve 34 opens, and liquid from chamber 29 escapes through the relief valve into the discharge pipe 37. The hydraulic pressure in openings 27 at this time is determined by the tension in the spring 35 of the relief valve.

The hydraulic pressure in the bores 45 of the cylinders 39 is determined, however, by the rate of descent of the pistons and the rate at which the liquid is permitted to escape thru the ducts 71 and orifices 81 into the chamber 72. The rate of descent of the pisof course, to the rate of descent of the ram 12, and since, in the press shown, the ram is crank operated, the rate of descent thereof reduces rapidly during the latter part of each down stroke. W'ith a View to maintaining a substantial pressure. within the cylinder bores 45 as the rate of descent of the pistons 50 reduces, the several ducts 71 of each group are disposed one above the other within the path of movement of the cooperating piston, so as to be successively blocked by the piston during its down stroke, thereby progressively throttling the escape of liquid from the cylinder bores 45. This progressive throttling compensates for the reduction in the rate of descent of the pistons, so that the hydraulic pressure in the cylinder bores 45 may be maintained substanially constant during the entire draw stroke. The liquid escaping through the ducts 71 passes into chamber 72, some of'it discharging through port 73 and pipe 75 into discharge passage 37, and the remainder passing upwardly through port 76 into the reservoir 23. Unless the pressure in bores 45' builds up sufficiently to overcome the hydra ulic pressure in chamber 29 and chambers 43 and the pressure of spring 49, valves 46 remain closed until opened by the contact of valves 63 against the rims 70 as thexpistons 50 approach the lower limit of their strokes.

. Figure 3 illustrates the position of piston 50 and valve 46 at the end of the draw stroke. In this position it will be noted that all the ducts 71 are blocked by the piston 50, and the lower end of the piston i sexposed to the full pressure in chamber 29 through ports 42.

This is the condition that exists at the in above described an upward return transmitted to the ring 15 through the knock out pins 16 is sufficient to break the finished work piece loose from the die. As the pressure plate 17, plungers 25, and pistons 50 rise, the check valve 33 opens and the pump 32 comes into pla to deliver liquid through pipe 31-into cham er 29, at constant pressure and at a ratecorresponding to the displacement'of the risin capacity. The vafires 46 close under the pressure of springs 49, as the pistons 50 rise, and thereafter the pressure plate 17 continues'to rise under the thrust of the plungers 25 alone. After valves 46 close, the entire discharge from the pump is directed to the openings 27 only,-and the rate of movement of the plate 17 increases accordingly. Since the rate of upward movement of the plate 17 is limited, however, by the volumetric capacity of the pump, the objectionable jump characteristic of spring or pneumatic pads is avoided. The pressure plate 17 rises into its tion against the bolster 11, and the ring 15 is thereby returned into work receiving position. a

The continued rise of the pistoiis 50 with the pressure plate 17 after the valves 46 close, produces a partial vacuum in the bores 45 of the cylinders, and the valves 63 open to thereby admit liquid under atmospheric pressure from the reservoir 23 through passages 62 into the bores. The bores 45 are thus maintained flooded so that when the pistons 50 and plate 17 have reached their upper limiting position, there is a solid body of liquid in each bore 45 capable of oiferin the resistance to the own stroke of the pistons on the next draw stroke. The excessive throttling of the liquid'by the orifices 81 and by the relief valve 34 develops considerable heat which may be dissipated by passing the dischargediliquid through pipe 37 to a radiator or condenser 90 of appropriate form. After passing through the radiator the liquid may be passed through an appropriate screeningtank' 91, and thence returned through piping 92 to asump in the base 93 of the pump. Any. liquid escaping thru the overflow turned to the sump through piping 94.

Various changes may be made inthe embodiment of the invention hereinabove described without departing from the invention as defined in the appended claims. 1 I claim a 1. A hydraulic pressure pad for draw pistons, up to full pump limiting posiport 24 may also be represses and the like comprisinga pressure member, pressure sustaining meansincluding a piston and cylinder, means permitting the escape of liquid from said cyhnder, and

means controlled by movement of said piston for throttling said escape means.

2. A hydraulic pressure pad for draw presses and the like comprising a pressure member, pressure sustaining means including a piston and cylinder, and a plurality of liquid discharge passages leading from said cylinder and controlled by said piston.

3. A hydraulic pressure pad for draw presses and the like comprising a pressure member, pressure sustaining means including a piston and cylinder, and a plurality of discharge passages leading from said cylinder. said passages being disposed within the path of movement of said piston and closed successively thereby.

4. A hydraulic pressure pad for draw presses and the like comprising a pressure member, pressure sustaining means including a piston and cylinder, :1 series of restricted passages in said cylinder permitting a restricted discharge of liquid therefrom, and means for closing one or more of said passages to thereby regulate the pressure in said cylinder.

5. A hydraulic pressure pad for draw presses and the like comprising a pressure member, pressure sustaining means includ ing a piston and cylinder, a series of restricted passages in said cylinder permitting a restricted discharge of liquid therefrom, and avalve for controlling said series of passages.

6. A hydraulic pressure pad for draw presses and the like comprising a pressure member, pressure sustaining means including a piston and cylinder, outlet means for said cylinder permitting a restricted discharge of liquid therefrom to thereby resist relative movement between said piston and cylinder in one direction, a hydraulic pressure source, and means for exposing said piston to said pressure source to etfect relative movement between said piston and cylinder in the'opposite direction.

7. A hydraulic pressure pad for draw presses and the like comprising a pressure member, pressure sustaining means including a piston and cylinder, outlet means for said cylinder operable to resist the discharge of-liquid therefrom, a hydraulic pressure source, and means'for opening said cylinder to said pressure source.

8. A hydraulic pressure pad for draw presses and the like comprising a pressure member, a. pressure sustaining member, pressure transmitting means between said members including a piston, a cylinder, a liquid reservoir in said pressure sustaining member, a pressure chamber in said pressure sustaining member, means through which liquid may be, admitted from said reservoir to said cylinder, outlet means from said cylinder to said reservoir, means for regulating the flow of liquid through said outlet means, and means for opening communication between said cylinder and said pressure chamber.

9. A hydraulic pressure pad for draw presses and the like comprising a pressure member, a pressure sustaining member, pres sure transmitting means between said members including a piston and cylinder, a liquid reservoir in said pressure sustaining member, a pressure chamber in said pressure sustaining member, means for admitting liquid from said reservoir to said cylinder, means permitting a restricted flow of liquid from said cylinder to said reservoir, and means controlled by said piston for opening and closing communication between said cylinder and said pressure chamber.

10. A hydraulic pressure pad for draw presses and the like comprising a pressure member, a pressure sustaining member having a liquid reservoir and a pressure chamber, and pressure transmitting means between said members, said means including a piston and cylinder open to said pressure chamber, a second piston, a cylinder, means for controlling'the discharge of liquid from said second cylinder and for admitting the same to said reservoir, means for admitting liquid from said reservoir to said second cylinder, and means controlled by said second piston for opening and closing communication between said second cylinder and said pressure chamber.

11. A hydraulic pressure pad for draw presses and the like comprising a pressure member, and means for applying pressure thereto comprising a piston and cylinder, a hydraulic pressure chamber, an open communication between said chamber and' said cylinder, a second piston and cylinder, discharge means operable to resist the escape of liquid from said second cylinder, and means controlled by movement of said second piston for opening and closing communication between said second cylinder and said chamber.

12. A hydraulic pressure pad for draw presses and the like comprising a pressure member, a hydraulic pressure chamber, a piston and cylinder open to said chamber for maintaining said member under pressure, a second piston and cylinder, and means for momentarily opening communication between said second cylinder and said chamber to increase the pressure on said member.

13. A hydraulic pressure pad for draw presses and the like comprising a pressure member, and hydraulic means operable to maintain a work clamping pressure thereon during the draw stroke ahd to provide a work stripping pressure during the return stroke, said hydraulic means includin a hydraulic pressure source, hydraulic: lly actuated means open to said pressure source during the entire stripping operation, and additional hydraulically actuated means open to said 1 f pressurev source during the initial portion tain a workclamping pressure thereon dur-' ing the draw strokeand to provide a work stripping pressure during the return stroke,

and means for rendering a portion of said hydraulic means ineffective after the initial portion of the stripping operation.

15. A hydrauliepressure pad for draw L presses and the like comprising a pressure member, and hydraulic means operable to Y maintain a work clamping pressure thereon 1 during the draw stroke and to provide a work strippingpressure during the return stroke,

said hydraulic means including a pump, hy-

draulically actuated means open to said pump during the entire return stroke, additional hydraulically actuated means open to said pump at the beginningof the stripping opering apiston and Cylinder. discharge means atlon, and meansfor closing communication between said pump and said additional means after the beginning of said stripping operation.

16. A hydraulic pressure pad for draw I presses and the like comprising a pressure member, pressure sustaining means includfor said cylinder operable to resist the escape of liquid therefrom, and means for cooling liquid discharged from said cylinder.

17. A hydraulic pressure pad for draw movement between said piston and cylinder v in one direction, and adjustable connections between said member and said piston and cylinder.

18. A hydraulic pressure pad for draw presses and the likecomprising a pressure member, a pressure sustaining member having a fluid reservoir therein. a cylinder in said member open at one end to said reseryoir, a piston in said cylinder connected with said pressure member. discharge means in the other end of said cylinder operable to resist the escape of liquid therefrom, said discharge means being open to said reservoir, and means for admitting liquid from the first mentioned end of said cylinder to said other end thereof.

19. A hydraulic pressure pad for draw presses comprising a blank holding and stripping member, a pressure sustaining member, hydraulic means for transmitting pressure between said members during the drawing operation to effect a work holding pressure, a pump, and direct hydraulic connections between said pump and means through which said means is operated at a rate corresponding to pump displacement during the stripping operation.

In Witnesswhereof, I hereunto subscribe my name this 9th day of June, .1926.

WALTER FERRIS. 

